1. Field of the Invention
The present invention relates, in general, to a kneading machine. More particularly, the invention relates to a kneading machine for automatically making bread.
2. Description of the Prior Art
Automatic bread making machines have, in general, three operating steps carried out automatically by a microcomputer. The first step is a kneading step in which main material, consisting of wheat flour mixed with sugar and salt, and water in a container is kneaded together with ancillary material, consisting of yeast, etc., to form bread dough. The second step is a fermentation step in which the bread dough is fermented. The third step is a baking step in which the bread dough is baked after the fermentation has finished. These steps are started and carried out automatically by pressing a start key, which constitutes the start element of a central device including the microcomputer. It typically takes about three hours to make bread from the start of the kneading step to the end of the baking step.
Recently, it has become desirable for people to obtain freshly-baked bread for breakfast or other meals. Therefore, a bread-making machine has been developed wherein the central device, including the microcomputer, has a timing function so that the desired bread making time can be set into the central device. This is accomplished by operating a timer key constituting a timer operating element of the central device, and pressing the start key, for example, at night. The bread making operation then starts about three hours before the desired time for obtaining freshly-baked bread.
The main material (wheat flour, mixed with sugar and salt, and water) and the ancillary material (yeast) must be placed in the container the preceding night when freshly baked bread is desired at breakfast. However, when the yeast comes into contact with the water, fermentation starts, and if the mixture of the yeast and the water is left alone for a long time before the kneading step, too much fermentation takes place. As a result the dough is denatured. Conventionally, therefore, the water and the yeast were separately maintained, so that they did not come into contact. Various schemes were adopted for mixing the water and yeast together at the start of the kneading step, for example, by using the rotation of a drive motor employed for kneading.
An example of such an automatic bread-making machine is disclosed in Japanese Utility Model Laid-Open Publication No. 57-155081, filed on Nov. 29, 1982 in the name of Shinji Takahagi. The automatic bread-making machine disclosed therein has a timer. Water is placed in a container having a valve which prevents the water from coming into contact with the yeast.
When the timer count reaches a set value, the valve is opened to mix the water with the yeast and the drive motor employed for kneading is driven, so that the bread-making operation starts. However, in these prior art bread-making machines, in spite of the above-mentioned various schemes, if a user pressed the start but forgot to operate the timer key, the drive motor for kneading would operate immediately, mixing together the separated water and yeast. In other words, these prior art bread-making machines have the possibility of the water and the yeast being mistakenly kneaded together at the wrong time.